Polymers based on acrylonitrile, butadiene and styrene, called ABS polymers for short in the plastics industry, are achieving increasing importance in the processing sector of the industry because of their excellent physical properties, particularly their great ductile strength and resistance to aging. However, their combustibility militates against further extension of their use. Efforts to reduce this high combustibility by the addition of flame-proofing agents have now shown that the flame-proofing agents normally used often with success in the case of other plastics materials are frequently ineffective in the case of poly-acrylonitrile and polymers containing acrylonitrile.
It is of course known that ABS polymers can be rendered flame-resistant with the aid of polyvinyl chloride. In this connection it is advantageous that polyvinyl chloride and ABS polymers are thoroughly compatible with each other. However, in order to achieve satisfactory flame-proofing, considerable quantities of the PVC additive are necessary - usually more than 30%. However, the readiness with which the ABS polymers can be processed and their physical properties are adversely affected by such great quantities of the additive.
It is also known that organic bromine compounds are in many cases considerably more effective as flame-proofing agents than are the corresponding chlorine compounds, so that in a given plastics material, considerably smaller quantities of a bromine compound are necessary compared to the quantity of the corresponding chlorine compound required to provide the same flame-proofing effects. Many known bromine containing flame-proofing agents for other polymers have proved virtually ineffective in low concentrations in ABS polymers.
The problem has therefore existed of finding a flame-proofing agent which is fully effective in ABS polymers in such small quantities that the physical and the chemical properties of the plastics material are virtually not changed by this additive.